I have a five year old Samsung 32" LCD HDTV. I will probably replace it in the next 12-18 months. If they make a 42-44" 4K UHDTV that is what I would probably lean towards because ist would go in my bedroom.
If you ask WHY woudl you buy a UHDTV in 2016/17? Well, because in the between 2016 and 2021 that will likely be what will be standard or useful....probably, it would be dumb to stick with 1080p in 2016.
4k is kind of wasted on a TV of that size, you'd have to be sitting really, really close to appreciate the difference. PC monitor close.